Refining beryllium in the presence of a flux



- reactions with the beryllium metal.

Patented Aug. 24, 1954 UNITED STATES @ATENT OFFICE REFINING BERYLLIUM INTHE PRESENCE OF A FLUX No Drawing. Application August 15, 1947, SerialNo. 768,935

2 Claims.

The present invention is concerned with the refining and casting ofberyllium metal using a new and novel refining flux composition.

An object of this invention is to produce beryllium metal castings of.substantially 99 per cent or higher chemical purity which are sound instructure and practically free of occluded gases.

Another object of this invention is directed toward a composition of arefining flux for melting and casting beryllium metal wherein saidrefining flux contains mixed compositions of beryllium, barium, calciumand lithium halides.

A further object of the invention is directed toward a method ofrefining and casting beryllium metal compositions whereby a moltenliquid flux containing fluorides of beryllium, calcium, barium, andlithium are admixed with the molten beryllium composition in ordertoproduce sound castings which are substantially free of occluded gases.

Other objects of the present invention will be apparent from thefollowing description.

In accordance with the present invention it has been found in refiningand casting beryllium metal compositions that by adding a molten liquidflux composition substantially free of moisture, wherein the fluxcomposition contains halide compounds of beryllium, barium, calcium, andlithium, to the melt, sound beryllium castings substantially free ofimpurities and occluded gases may be produced. In addition, it was foundthat the chemical composition and the physical structure of theseberyllium castings were substantially improved by the incorporation oflithium fluoride with the fluorides of beryllium, calcium and barium.

In general, when refining and casting light metals, a group whereinberyllium metal is defined, it is not generally considered desirablefrom a metallurgical standpoint to'have strong agitation in the lightmetal melt as this action tends to admix the oxides and impurities withthe metal rather than to permit the metal and the impurity to separate.Therefore it is important that the motor agitation produced in a melt bereduced to a minimum. Various refining flux compositions for melting andcasting pure beryllium metal were used at temperatures in excess of 2600F., and it was found that these fluxes fumed excessively and producedviolent chemical These flux compositions generally contained admixturesof mixed halides of the alkaline earth metals and the alkali metalgroups, such as the fluorides and chlorides of beryllium, calcium,barium, magnesium, sodium potassium, and lithium metals. When a fluxcomposition contains various mixtures of these halide compounds, such asthe fluorides of beryllium, calcium, and barium metals, a violentreaction occurs in the beryllium melt which necessitates adding the fluxvery slowly in order to keep the molten beryllium within the confines ofthe crucible. This violent reaction and agitation within the melt tendsto admix the oxides and impurities of the melt with the beryllium metal;and upon casting the beryllium melt, the resultant castings were foundto be unsound and contained impurities and occluded gases. However, whena lithium halide, preferably lithium fluoride, is added in combinationwith an admixture of beryllium fluoride, barium fluoride and calciumfluoride, the characteristic violent reaction with the molten berylliummetal is substantially reduced; and it was found that the fluxcomposition could be added very rapidly to the beryllium melt with verylittle reaction. In addition, it was found that the fiux composition ofthe present invention containing lithium fluoride is also a betterrefining flux because the resulting castings are very pure, sound andpractically free of occluded gases.

By the addition of a lithium halide, preferably lithium fluoride, to afiuxing admixture containing fluorides of beryllium, calcium, and bariummetals there is provided a new and novel method for melting and castingberyllium metal. This new and novel melting practice for producingberyllium castings consists of melting beryllium in a crucible,preferably a silicon carbide crucible, in the presence of an inertatmosphere, preferably argon, and then introducing into the melt arefining fiux in molten liquid form containing fluorides of beryllium,calcium, barium, and as the improvement about 7 to 20 per cent by weightof lithium fluoride. The beryllium metal used in the melting proceduremay contain virgin metal, scrap and remelted beryllium metal. Virginberyllium metal when used as received generally assays about per centberyllium, the balancev being slag and mixed oxides. Remelted berylliumand the scrap introduced in corresponding melts suitably contain about86 per cent beryllium. It was found that by utilizing the refining andcasting procedure of the present invention in conjunction with the novelflux composition containing lithium fluoride, beryllium castings havinga purity approaching 99 per cent may be obtained. In addition, thesecastings are sound and practically free of occluded gases.

The proportion of the constituents of the flux composition may be variedover a relatively wide range. The proportional percentage composition ofthe compounds comprising the total flux composition may be identified inthe following table:

Table Per cent by Weight Beryllium fluoride 45-65 Calcium fluoride 7-20Barium fluoride 7-20 Lithium fluoride 7-20 A preferred flux compositionof the present invention may contain approximately 4 parts by Weight(57%) of beryllium fluoride, 1 part by weight (14%) of calcium fluoride,1 part by weight (14%) of barium fluoride and about 1 part by weight(14%) of lithium fluoride.

A typical remelting and refining cycle may be illustrated in thefollowing manner: A beryllium metal composition is introduced into asilicon carbide crucible; and the loaded crucible is then inserted intoan induction furnace utilizing a purified argon atmosphere. The melt isthen raised to a temperature of approximately 2300 to 2700" F. for aperiod of time in order to allow the melt to come to a completely moltencondition. The flux composition containing 4 parts by weight ofberyllium fluoride, 1 part by weight of calcium fluoride, 1 part byweight of barium fluoride, and 1 part by weight of lithium fluoride ismelted in a separate graphite crucible in order to eliminate moisturecontent present in the flux admixture. The molten flux is then added tothe beryllium melt and no violent reaction is observed. The berylliummelt containing the flux composition is then cast into graphitetransverse bar molds at a temperature of about 2600 to 2700 F. Theresulting castings are sound and possess a well defined grain structure.The physical properties of the metal are excellent and the metalrecovery approaches 87 per cent. Spectrographic analysis of theberyllium metal melted by this method showed highly pure beryllium metalwith not a trace of lithium. Since beryllium metal may be used as amoderator in the construction of neutronic reactors, the presence oflithium Would be highly objectionable due to its high neutron capturecross section.

It will be apparent to those skilled in the art to which this inventionpertains that various modifications may be made without departing fromthe principles of the invention as disclosed herein, and thus it is notintended that the invention should be limited other than by the scope ofthe appended claims.

What is claimed is:

1. A method of producing beryllium castings which comprises meltingberyllium in the presence of an inert atmosphere, admixing with theberyllium melt a molten refining flux composition containing -65% ofberyllium fluoride, about 7-20% of barium fluoride, about 7-20% ofcalcium fluoride, and about 7-20% of lithium fluoride at a temperatureof about 2300 F., and then casting the molten beryllium metal at atemperature in excess of the melting point of beryllium metal.

2. A method of producing beryllium castings which comprises meltingberyllium in the presence of an argon atmosphere, admixing with theberyllium melt a molten refining flux composition containing 57% ofberyllium fluoride, about 14% of barium fluoride, about 14% of calciumfluoride, and about 14% of lithium fluoride of the combined fluxcomposition at a temperature of about 2300 F., and then casting theresultant beryllium melt at a temperature of about 2700 F.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 394,742 Webster Dec. 18, 1888 1,511,829 Dickinson Oct. 14,1924 1,673,043 Fischer June 12, 1928 1,775,589 Cooper Sept. 9, 19302,052,278 Callis et al Aug. 25, 1936 2,148,664 Wille et al Feb. 28, 1939

1. A METHOD OF PRODUCING BERYLLIUM CASTINGS WHICH COMPRISES MELTINGBERYLLIUM IN THE PRESENCE OF AN INERT ATMOSPHERE, ADMIXING WITH THEBERYLLIUM MELT A MOLTEN REFINING FLUX COMPOSITION CONTAINING 45-65% OFBERYLLIUM FLUORIDE, ABOUT 7-20% OF BARIUM FLOURIDE, ABOUT 7-20% OFCALCIUM FLOURIDE, AND ABOUT 7-20% OF LITHIUM FLOURIDE AT A TEMPERATUREOF ABOUT 2300* F., AND THEN CASTING THE MOLTEN BERYLLIUM METAL AT ATEMPERATURE IN EXCESS OF THE MELTING POINT OF BERYLLIUM METAL.